Cutting saws come in numerous shapes and sizes and, from hacksaws to hand-held electrically-powered circular saws to large industrial table saws, are used for a variety of applications. Many varieties of saws are used by people in home maintenance and home improvement projects. These and other kinds of saws also are often indispensable tools for carpenters, construction workers, and the like. Large saws often are automated and used in heavy industrial situations. Regardless of shape, size or application, these devices have one thing in common: the saws allow one to take a piece or section of material that is often large, bulky and unmanageable and cut it into smaller pieces or sections suited for specific applications.
The surfaces on which these cutting saws are used are as varied as the kinds of saws themselves. Although one usually associates the use of saws with wood, saws are also used to cut plastic, metal and concrete. Many saws are capable of cutting several types of materials, while other more specialized saws are suited more for a single type of material. However, the type of material that a saw is intended to cut usually determines the kind of blade with which the saw is equipped.
One problem associated with cutting wood or similar fibrous materials with a conventional multi-purpose blade is the splintering effect of the blade as it cuts through the material. Conventional blades tend to rip through the material. A rough cutting edge is the end result because of the tearing effect on the material due to the ripping characteristics of the blade; that is, the blade does not cut all fibers cleanly. Rather, many of the fibers, especially as the saw blade initially enters the surface of the material, are torn and not cut. This results in a splintering or shredding of the material. The surface must then be sanded or otherwise smoothed and repaired. This added step results in increased cost, both in labor and in time. Often, if the surface was a finished surface before the cutting, irreparable damage may be caused by the saw.
In order to avoid this problem, a multiple parallel blade design has been proposed, as shown in U.S. Pat. No. 4,641,562. In a typical multiple blade arrangement, a longer blade (or blades) makes an initial rough ripping cut through the surface, followed by the smoother, more refined cutting action of a second blade (or blades). The blade making the initial cut contains teeth of a uniform length, and of a design well known to those skilled in the art, to facilitate the initial cut. The top outer edges of the outer cutting blade are the points of initial contact of the blade configuration with the surface. The initial transverse pressure exerted on the surface of the material by the top outer edges causes penetration of the surface by the blade edge into the material.
Alternatively, if the application is for cutting a soft, highly fibrous material such as palm wood wherein the fibers are more loosely associated than in other kinds of wood, a blade as disclosed in U.S. Pat. No. 3,181,577 may be used. Because of the softness of the surface and the lack of a need for an initial piercing blade edge to penetrate the softer, more easily penetrable surface, thin continuous parallel radial cutting edges are used for the initial cut. The continuous edges are knife-like in action and actually produce a slicing effect, while the teeth between the parallel outer blades carry away the severed bits of material. The knife-like outer blades initially slice the fibers and allow for easier cutting by the teeth. If a conventional blade were used to cut such a soft material, increased manual pressure would have to be applied to the saw itself because the fibers initially yield to a normal ripping saw blade before breaking.
However, problems are associated with these blades with pre-cutting edges. One problem associated with these blades is that a continuous pre-cutting edge as in U.S. Pat. No. 3,181,577 is not effective on harder surfaces that are more difficult to penetrate. Surfaces harder than palm wood require an edge that initially bites into the surface, allowing the remainder of each tooth to follow the initial penetration into the material. Without this initial biting action, a knife-like pre-cutting blade requires an operator to exert significantly more manual pressure on the blade to initially penetrate the material. This action causes much more wear on the blade itself through the additional pressure on the blade.
Further, pre-cutting blades of uniform radial length, while minimizing splintering and shredding, tend to accumulate with the cut fibrous material. For example, a blade with parallel pre-cutting blades of uniform length used to cut a plastic surface heats the cut plastic due to the friction involved during the cutting process. The plastic tends to partially melt and adhere to the blades. This partial melting clogs the blades, reducing their effectiveness and causing an increase in both job time and labor because one must periodically stop to clear the material from the blades. Blade designs, such as the designs disclosed in U.S. Pat. Nos. 4,641,562 and 3,181,577, if used on a wood surface, could experience similar clogging problems caused by the accumulation of cut wood particles.
Thus, there is a need for a blade with pre-cutting edges that minimizes splintering or shredding of the cut material and at the same time minimizes clogging of the blade with the cut material.
Another problem associated with prior saw blades with pre-cutting edges is that the outer pre-cutting edge of a blade tooth that makes the initial penetrating cut into the surface enters the material through the initial piercing action of the edge. The rest of the tooth follows the leading edge and finishes the cut of that particular tooth. Because each particular tooth on the blade has a single initial point of contact, the remainder of the tooth surface that follows the leading edge tends to rip, rather than slice, the material. This characteristic hinders these particular blades with pre-cutting edges because the problems that the blades are supposed to address--splintering and rough edges--remain to some extent.
Thus there is a need for a blade with pre-cutting edges that further reduce splintering and rough edges of the workpiece caused by the pre-cutting blade edges.
In light of these aforementioned needs, it is therefore an object of the present invention to provide an improved saw blade.
It is a further object of the invention to provide a saw blade that minimizes splintering or shredding of the material being cut.
It is another object of the invention to provide a saw blade that minimizes clogging of the blade with the material being cut.
It is a further object of the invention to provide a blade with pre-cutting edges that further reduce splintering and rough edges of the material being cut.